The invention relates to a sealing arrangement for the sealing-off of spaces acted upon by media of different pressures, such as fluids and/or gases, particularly for turbomachinery, said arrangement including sealing ring means arranged in a cylindrical housing device while forming a secondary seal and being disposed with respect to an adjacent rotor section to form a radial sealing gap means as a primary seal.
It is still difficult in practice to ensure a no-contact operation for sealing devices of the initially mentioned type and to construct them with a relatively low overall height; specifically between rotating and stationary components or shaft sections or between components or shaft sections which rotate around a common axis at different rotational speeds.
Although generally known labyrinth sealing devices have the advantage that they operate axially and radially practically without any contact and permit almost unlimited circumferential speeds, these advantageous characteristics are counteracted by the significant disadvantages of a relatively large axial overall length as well as of relatively high seal leakage flows.
For the mentioned sealing purposes, brush sealing devices are generally known, the bristle ends of which are firmly anchored at a stator and the other free bristle ends of which are directed in sliding contact against the rotor or a shaft section. Although such brush sealing devices permit high circumferential speeds and allow a short axial overall length, they require a large radial installation height and, as a result of continuous abrasive contact, cause a wearing-off of the bristles and a local abrasion of the material at the corresponding countersurface of the rotor.
Radial sliding ring sealing devices are also known which comprise a housing; a sliding ring; an element which is elastic in axial direction; and the pertaining shaft or the pertaining shaft section. The primary seal is therefore constructed between the corresponding inner surface of the sliding ring and the countersurface of the rotor or of a shaft section, specifically by way of the fluid gap which is generated in this case as a result of the pressure difference between two spaces to be sealed off. In the case of this known sliding ring sealing device, the sliding ring is sealingly guided, for example, between a supporting shoulder of the housing on one side and a movable spring plate for example on the other side which has the effect of the spring element (secondary seal).
Such "simply" constructed sliding ring sealing devices cannot meet perfect sealing requirements when they have the purpose of sealing off, for example, storage space in gas turbine engines with respect to the engine inlet or the engine environment or with respect to the exhaust gas flow, thus localities which normally have a lower pressure level than the storage space in front of the sealing device. In addition, sliding ring sealing devices require a large installation volume and ensure only low circumferential speeds.
An object of the invention is to provide an arrangement of the initially mentioned type which, while ensuring relatively high circumferential speeds, with a comparatively low installation height and a relatively small installation volume, operates practically without any wear and without any abrasion of material.
The object is achieved according to certain preferred embodiments of the invention by providing an arrangement wherein the sealing ring means are centered by means of bending-rod-type spring element means which are anchored on one side at the cylindrical housing device and are arranged essentially in parallel to the machine axis, and wherein the radial sealing gap means between the sealing ring means and adjacent rotor section are dimensioned such that they form an air-bearing-type bearing gap with respect to a given pressure difference (P1 &gt;P2) between two machine spaces.
The sealing arrangement according to the invention avoids the essential disadvantages of the initially mentioned types of sealing devices.
According to the invention, a sealing arrangement is therefore obtained in which, in the area of the sealing point, a sealing ring is arranged concentrically with respect to the shaft such that a radial gap is generated between the shaft and the sealing ring which is small and which is constructed in the size which is customary in air bearings. This has the result that the sealing ring, like an air bearing, follows static and dynamic axial deviations. This gap between the sealing ring and the shaft defines the so-called "primary leakage" of the sealing device. The sealing ring itself, by way of a connection of bending rod springs which are essentially parallel to the seal axis or are arranged at a certain angle with respect to the seal axis, is centered, for example, with respect to the stator of the sealing device, in which case the length and the number of the bending rod springs depend on the dynamics of the machine at the sealing point. An axial gap is arranged between the stator of the sealing device and the sealing ring, either on a diameter inside and/or outside the diameter of the bending rod connection, this axial gap being as small as possible (size 0.02-0.03 mm) and determining the so-called "secondary leakage" of the sealing device. Around the mentioned elements of the sealing device, a cylindrical protective cap or a hood-type body is arranged which, as required, can be formed by the components at which the sealing device is to be arranged. Depending on the flow direction of the sealing device (P1 &gt;P2 or P2 &gt;P1), a bonding of the bending rod connection with the sealing ring is advantageous by means of a known bonding technique, such as welding, soldering, gluing or clamping.
Depending on the dynamic conditions, the mentioned bending rod connection may be constructed of individual free-standing bending rods (FIG. 6, like the spring, without any damper) or of a brush-type packed connection of rods (FIG. 7) which rest against one another (spring plus damper).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.